Electromagnetic fuel pump



Sept. 13, 19 1.. c. PARKER 2,717,553

ELECTROMAGNETIC FUEL PUMP Filed Sept. 29, 1952 INVENTOR. (k/(212d C. War/ier WITNESS A TORNEY United States atent Ofilice 2,717,553 Patented Sept. 13., 1955 ELECTROMAGNETIC FUEL PUMP Leland C. Parker, Elmira, N. Y., assignor to Bendix Aviation Corporation, a corporation of Delaware Application September 29, 1952, Serial No. 312,050 Claims. (Cl. 103-25) The present invention relates to an electromagnetic fuel pump and more particularly to a piston type pump in which the piston is reciprocated at a substantially con stant frequency, variation of the output being secured by varying the stroke of the piston.

It is an object of the present inventionto provide a novel fuel pump of the character indicated incorporating simple and effective contact mechanism for periodically actuating the electromagnet.

It is another object to provide such a device in which the flux of the electromagnet is conducted by the pump piston to make it effective to open the contacts and thereby deenergi'ze the electromagnet.

It is a further object to provide such a device incorporating a pressure responsive switch mechanism for rendering the pump inoperative when a predetermined maximum output pressure is exceeded.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which the figure is a vertical, substantially mid-sectional view of a preferred embodiment of the invention.

in the drawing there is illustrated a cylinder 1 of nonmagnetic material which connects the input chamber 2 and the output chamber 3 of a generally cylindrical casing 4 forming the housing of the pump. A solenoid 5 surrounds a portion of the cylinder 1 and is confined thereon by means of pole pieces 6 and '7 which serve to locate the cylinder and solenoid coaxially within the housing 4. A hollow piston 8 of magnetic material is slidably mounted in the cylinder 1 and is normally maintained in a decentered relation to the solenoid 5 by means of springs 9 and 11.

A check valve 12 is mounted in a cup 13 attached as indicated at 14 to the under side of the pole piece 7, and a second check valve 15 is mounted in the lower end of the piston 8 whereby reciprocation of the piston transfers fluid from the intake chamberZ to the outlet chamber 3.

Means for periodically energizing the solenoid 5 to cause reciprocation of the piston 8 is provided including a battery 16 grounded at 7 and connected through a manual switch 18, a normally closed pressure sensitive switch 19 and a pair of normally closed contacts 21 and 22 to one end of the solenoid 5, the opposite end of which is grounded as indicated at 23 to complete the circuit. Contacts 21 and 22 are pendulously mounted on spring plates or reeds 24 and 25 respectively, which reeds are mounted adjacent the upper end of the cylinder 1 and insulated therefrom and from each other as shown at 26. The lower end of the reed 25 carrying the contact 22 has fixed thereon an armature in the form of a block of soft iron 27 which, as illustrated, is supported by the reed in proximity to a portion of the cylinder 1 occupied by the end of the piston 8 which projects above the upper pole piece 6 of the solenoid. By this arrangement, when the solenoid is energized, some of its flux is conducted by the piston 8 to form a field which attracts the armature 27, bending the reed 25 away from the reed 24. The elasticity of the reed 24 permits it to follow the reed 25 for a short distance, after which the continued movement of the reed 25 as actuated by the armature 27 moves the contact 22 out of engagement with the contact 21, thus breaking the solenoid circuit. The following movement of the reed 2 1 may be adjustably limited by means of a pin 30 extending eccentrically from a stud 30' rotatably mounted in the shell of the housing 4.

Means are preferably provided for rendering the pump inoperative when a predetermined maximum pressure in the output chamber 3 is exceeded. For this purpose, a flexible diaphragm 28 is arranged to form a closure for the chamber 3, being sealed on the upper end :of the housing 4 by means of a cup-shaped member 29 having a flange 31 crimped around an outturned flange 32 on the end of the housing 4. The diaphragm 28 is soldered or brazed around its periphery to .a backing plate 33 which is fixed in the rim of the cup member 29:, and is provided with vertically extending threaded posts 34 and 35 on which the frame 36 of the pressure responsive switch 19 is adjustably mounted .as. by means of nuts 37 and 38.

Switch 19 is a normally closed snap switch of commercial form having an actuating arm 39 which extends to a point opposite the central portion of the diaphragm 28. A plunger 41 is slidably mounted in the backing plate 33 and connects the diaphragm to the switch arm in such manner that upward deflection of the diaphragm beyond a predetermined point will move the arm 39 to open the switch 19.

In operation, starting with the parts in the positions illustrated, closure of the manual switch 18 completes the circuit through the pressure responsive switch 19 and normally closed contacts 21, 22 to the solenoid 5 which accordingly magnetizes and draws the piston 8 downwardly against the force of the spring 9. At the same time, the magnetic field around the upper end of piston 3 attracts the armature 27, bending the reed 25 away from the reed 24 and opening the contacts 21, 22 when the following movement of the reed 24 is arrested. The consequent deenergization of the solenoid 5 permits the spring 9 to return the piston 8 to its normal position, and concurrently permits contacts 21, 22 to close. The piston 8 is thus caused to reciprocate in time with the pendulous movement of the armature 27 on the reed 25, which reciprocation is effective by virtue of the check valves 12 and 15 to draw fluid from the inlet chamber 2 and discharge it into the outlet chamber 3.

When this device is used to supply fuel to the carburetor of an internal combustion engine, the withdrawal of fuel from the output chamber 3 is, of course, dependent upon the current requirements of the engine. The pressure in the output chamber is accordingly quickly built up by the actuation of the pump to the predetermined maximum point, at which time the diaphragm 28 flexes upwardly, moving the arm 39 to open the switch 19 and thus render the pump inoperative until such time as the pressure in the output chamber is again reduced by withdrawal of fuel therefrom.

It will be noted that in the above described structure, the frequency of reciprocation of the pump piston is determined by the natural period of vibration of the reed 25 carrying the armature 27. The length of stroke of the pump piston is determined by the volume of fluid allowed to escape from the discharge chamber 3.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and changes may be made in the design and arrangement of parts without departing from the spirit of the invention.

I claim:

1. In an electromagnetic pump, a casing of magnetic material having inlet and outlet chambers, a non-magnetic cylinder in the casing connecting said chambers, a hollow magnetic piston slidably mounted in the cylinder, a solenoid surrounding the cylinder, a spring urging the piston toward a decentered position with respect to the solenoid, means for periodically energizing the solenoid including a pair of contacts, means for penduiousiy mounting one of said contacts for movement into and out of engagement with the other contact, an armature fixed on said mounting means adjacent to but spaced from the piston, and so arranged that the attraction of the piston for the armature when the piston is magnetized by the solenoid draws the pendulously mounted contact away from the other contact; said mounting means including resilient means for closing the contacts responsive to demagnetization of the solenoid and piston; and means including a check-valve in the piston operative to transfer fluid from the inlet chamber to the outlet chamber responsive to reciprocation of the piston.

2. An electromagnetic pump as set forth in claim 1 in which said mounting means includes a pair of elastic reeds on which said contacts are mounted, and said armature is mounted on one of said reeds in position to move away from the other reed and open the contacts responsive to flux of the solenoid conducted by the piston.

3. An electromagnetic pump as set forth in claim 2 including further adjustable stop means for said other reed limiting its travel with the armature carrying reed.

4. An electromagnetic pump as set forth in claim 1 including further means responsive to a predetermined fluid pressure in the output chamber for preventing energization of the solenoid.

5. An electromagnetic pump as set forth in ciaim 4 in which the pressure-responsive mechanism for control iing the operation of the pump comprises a flexible diaphragm forming a closure for the output chamber, a normaily-closed snap switch having an actuating arm extending into proximity to the center of the diaphragm, a plunger transmitting movement of the diaphragm to the switch arm, and mounting means for the switch adjustable to move the switch arm toward and away from the diaphragm to regulate the pressure in the output chamber required to open the switch.

References Cited in the file of this patent UNITED STATES PATENTS 

